The trial of an alleged German neo-Nazi accused of involvement in a 10-person killing spree has been adjourned after the defence team accused the judge of bias.

Judge Manfred Goetzl put proceedings on hold until May 14 to consider the defence request that he recuse himself from the court case.

It is the highest-profile neo-Nazi murder trial in Germany in decades and could last at least a year.

Beate Zschaepe, said to be the sole surviving member of a gang behind the murders, had entered the court in a dark suit, her arms folded, before turning her back to the cameras and appearing to joke with her lawyers.

Uwe Mundlos (L) and Uwe Boenhardt

Her trial began with two motions from the defence lawyers alleging judicial bias.

Zschaepe, 38, is accused by prosecutors of murder for alleged complicity in the killing of eight Turks, a Greek and a policewoman between 2000 and 2007.

If convicted, she faces life imprisonment. Four others face lesser charges of assisting the cell.

Zschaepe handed herself in to police in November 2011

Zschaepe is also accused of involvement in at least two bombings and 15 bank robberies allegedly carried out by her accomplices, Uwe Mundlos and Uwe Boenhardt, who died in an apparent murder-suicide in November 2011.

Prosecutors allege the trio had formed the self-styled National Socialist Underground (NSU) after evading arrest on lesser charges in 1998 and managed to remain largely off the authorities' radar for the following 13 years despite committing a string of violent crimes.

Hundreds of reporters lined up outside the Munich courthouse in the hope of gaining one of the few available seats in the packed courtroom.

Aside from Zschaepe, four other defendants are accused of crimes relating to the NSU's activities.

Beate Zschaepe in court

Like Zschaepe, the co-defendants were known to German authorities before the existence of the NSU - whose name alludes to the official name of Adolf Hitler's National Socialist German Workers' Party - came to light.

Many of Germany's three million residents of Turkish descent have asked how the country's well-funded security services, with their network of informants in the far-right scene, could have overlooked the group's existence for so long.

For years, police suspected the immigrant victims of being involved with foreign gangs linked to gambling and drugs.

Families of those killed and survivors of the bomb attacks in particular have said they are hoping not just for justice, but answers to questions such as how the group chose its victims, none of whom were high-profile targets.

Her lawyers have said she will remain silent during the lengthy trial.

Under German law Zschaepe will not have to make a plea until the end, though her lawyers have said they will contest the prosecution charges.